The test program runs and expects many, many ENOENTS to be returned. It just doesn't expect ESTALE to be returned. It doesn't see ESTALE from local file systems. To answer a question asked earlier -- the test program does not mimic any particular application behavior, except in the extreme. It is designed to create as stressful a situation as might be ever seen. Has anyone explained why the full solution won't work from a technical viewpoint? Thanx... ps -----Original Message----- From: Steve Dickson [mailto:SteveD@xxxxxxxxxx] Sent: Monday, April 23, 2012 10:55 AM To: Jeff Layton Cc: linux-fsdevel@xxxxxxxxxxxxxxx; linux-nfs@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; miklos@xxxxxxxxxx; viro@xxxxxxxxxxxxxxxxxx; hch@xxxxxxxxxxxxx; michael.brantley@xxxxxxxxxx; sven.breuner@xxxxxxxxxxxxxxxxxx; chuck.lever@xxxxxxxxxx; Peter Staubach; malahal@xxxxxxxxxx; bfields@xxxxxxxxxxxx; trond.myklebust@xxxxxxxxxx; rees@xxxxxxxxx Subject: Re: [PATCH RFC v3] vfs: make fstatat retry once on ESTALE errors from getattr call On 04/20/2012 05:13 PM, Jeff Layton wrote: > On Fri, 20 Apr 2012 16:18:37 -0400 > Steve Dickson <SteveD@xxxxxxxxxx> wrote: > >> On 04/20/2012 10:40 AM, Jeff Layton wrote: >>> I guess the questions at this point is: >>> >>> 1) How representative is Peter's mkdir_test() of a real-world workload? >> Reading your email I had to wonder the same thing... What application >> removes hierarchy of directories in a loop from two different clients? >> I would suspect not many, if any... esp over NFS... >> > > Peter's test just happens to demonstrate the problem well, but one > could envision someone removing a heirarchy of directories on the > server while we're trying to do other operations in it. At that point, > we can easily end up hitting an ESTALE twice while doing the lookup > and returning ESTALE back to userspace. Just curious, what happens when you run Peter's mkdir_test() on a local file system? Any errors returned? I would think removing hierarchy of directories while they are being accessed has to even cause local fs some type of havoc > >>> >>> 2) if we assume that it is fairly representative of one, how can we >>> achieve retrying indefinitely with NFS, or at least some large >>> finite amount? >> The amount of looping would be peer speculation. If the problem can >> not be handled by one simple retry I would say we simply pass the >> error up to the app... Its an application issue... >> > > It's not an application issue. The application just asked the kernel > to do an operation on a pathname. The only reason you're getting an > ESTALE back in this situation is a shortcoming of the implementation. > > We passed it a pathname after all, not a filehandle. ESTALE really has > no place as a return code in that situation... We'll have to agree to disagree... I think any application that is removing hierarchies of file and directory w/out taking any precautionary locking is a shortcoming of the application implementation. > >>> >>> I have my doubts as to whether it would really be as big a problem >>> for other filesystems as Miklos and others have asserted, but I'll >>> take their word for it at the moment. What's the best way to contain >>> this behavior to just those filesystems that want to retry >>> indefinitely when they get an ESTALE? Would we need to go with an >>> entirely new ESTALERETRY after all? >>> >> Introducing a new errno to handle this problem would be overkill IMHO... >> >> If we have to go to the looping approach, I would strong suggest we >> make the file systems register for this type of behavior... >> > > Returning ESTALERETRY would be registering for it in a way and it is > somewhat cleaner than having to go all the way back up to the fstype > to figure out whether you want to retry it or not. How would legacy apps handle this new errno, esp if they have logic to take care of ESTALE errors? steved. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
